Troubleshooting Trailer Wiring that Works with One Tow Vehicle but Not Another

Question:

I rewired a small utility trailer I have not lights on the trailer when hooking up to my 2005 trailblazer. I can hook up another vehicle to the same trailer and everthing works. IV replaced most of the fuses in the panel in the trailblazer pertaining to lighting even though they were still good but still no lights. Need some help please. Thank you for your thoughts

asked by: Al

Expert Reply:

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

If the voltage checks out here and the trailer still does not work with your Trailblazer you will want to check the main ground of the trailer wiring on the trailer first. Sometimes a weak ground on the trailer can cause the lights not to function which certain tow vehicles.

If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well.

I attached a couple help articles on trailer wiring for you to check out as well.

expert reply by: Jameson C